Realtime monitoring and analysis of heart-beat dynamics

Abstract

A system for estimating a statistic associated with a cardiac signal having periodic events includes a clock and a digital filter. The clock determines an extent of a censored interval beginning at a most recent event and ending at a time selected from a continuum of times. The digital filter implements a point process stochastic model of the cardiac signal, receives the censored interval, and estimates the statistic at least in part on the basis of historical data and the censored interval.

1 . A method for estimating a statistic associated with a cardiac signal having periodic events, the method comprising: 
 defining a point process stochastic model of the cardiac signal; 
 selecting, from a continuum of times, a selected time at which to estimate the statistic;  
 determining an extent of a censored interval that begins with a most recent one of the events and ends at the selected time; and  
 on the basis of the point process model and the extent of the censored interval, computing an estimate of the statistic at the selected time.  
   
   
   
       2 . The method of  claim 1  further comprising selecting the stochastic model to have a history-dependent inverse Gaussian probability density function.  
   
   
       3 . The method of  claim 1 , further comprising estimating a parameter associated with the stochastic model at least in part on the basis of a history of intervals.  
   
   
       4 . The method of  claim 3 , wherein estimating a parameter comprises computing a maximum likelihood estimate.  
   
   
       5 . The method of  claim 3 , further comprising recursively updating the parameter estimate.  
   
   
       6 . The method of  claim 1  further comprising selecting the physiologic signal to be a signal derived from fetal heart rate.  
   
   
       7 . The method of  claim 3 , further comprising selecting the number of intervals to be between two and five.  
   
   
       8 . A system for estimating a statistic associated with a cardiac signal having periodic events, the system comprising: 
 a clock for determining an extent of a censored interval beginning at a most recent event and ending at a time selected from a continuum of times; and    a digital filter for implementing a point process stochastic model of the cardiac signal and receiving the censored interval, the filter being configured to estimate the statistic at least in part on the basis of historical data and the censored interval.    
   
   
       9 . The system of  claim 8 , further comprising a signal source for providing the cardiac signal.  
   
   
       10 . The system of  claim 9 , wherein the signal source comprises an electrocardiograph.  
   
   
       11 . The system of  claim 9 , wherein the signal source comprises a fetal heart rate monitor.  
   
   
       12 . The system of  claim 8 , wherein the digital filter is configured to receive the historical data.  
   
   
       13 . The system of  claim 12 , wherein the digital filter is configured to implement a stochastic model having a history dependent inverse Gaussian probability density function.  
   
   
       14 . A computer-readable medium having encoded thereon software for estimating a statistic associated with a cardiac signal having periodic events, the software including instructions for causing a computer to: 
 define a point process stochastic model of the cardiac signal; 
 select, from a continuum of times, a selected time at which to estimate the statistic;  
 determine an extent of a censored interval that begins with a most recent one of the events and ends at the selected time; and  
 on the basis of the point process model and the extent of the censored interval, compute an estimate of the statistic at the selected time.  
   
   
   
       15 . The computer-readable medium of  claim 14 , wherein the software further comprises instructions for causing a computer to select the stochastic model to have a history-dependent inverse Gaussian probability density function.  
   
   
       16 . The computer-readable medium of  claim 14 , wherein the software further comprises instructions for causing a computer to estimate a parameter associated with the stochastic model at least in part on the basis of a history of intervals.  
   
   
       17 . The computer-readable medium of  claim 16 , wherein the instructions for estimating a parameter comprise instructions for computing a maximum likelihood estimate.  
   
   
       18 . The computer-readable medium of  claim 16 , wherein the software further comprises instructions for causing a computer to recursively update the parameter estimate.  
   
   
       19 . The computer-readable medium of  claim 14 , wherein the software further comprises instructions for causing a computer to select the physiologic signal to be a signal derived from fetal heart rate.  
   
   
       20 . The computer-readable medium of  claim 16 , wherein the software further comprises instructions for causing a computer to select the number of intervals to be between two and five.